Heretofore, when boring tunnels through earth such as for accommodating pipes and the like which extend under roads, such as normally done by an earth boring machine. These machines would be mounted on rails so that the auger associated with the boring machine drilled a hole into the earth, the machine could be shifted forward on the rails. The auger would rotate within an elongated sleeve and normally a hydraulically operated cylinder would force the sleeve into the embankment and the auger sould remove the dirt as such was forced forward. One problem with such devices is that when the sleeve would strike a rock formation, it was necessary to remove the sleeve from the hole being bored and the auger inserted back in with a cutting head for cutting through the rock formation. Such a method was time-consuming.
The reason it is necessary to rotatably mount the auger within the elongated sleeve is to ensure a true and level hole is bored through the embankment. If the sleeve were not present, the rotational force of the auger would tend to cause the auger to follow a direction which would be downwardly and to the right of the desired central axis of the hole or tunnel being bored.
Whn it is necessary to remove the sleeve in which the auger is rotating during the boring operation as a result of striking rocks and the like, it is difficult to reinsert the sleeve back in the identical hole. Furthermore, such is a time-consuming operation.